1. Field of the Invention
This invention is directed to a method of naturally drying mining and metallurgical pulps. It refers, more particularly, to the treatment of pulps the solid fraction of which has as d.sub.80 of less than 100 microns and, by preference, of less than 20 microns. The d.sub.80 is the smallest mesh so which 80% of the product is able to pass.
2. Description of the Prior Art
Such pulps occur very frequently in numerous fields of the mining and metallurgical industries. Slimes of this type may also be produced during the treatment of waste water for the purpose of purifying the water.
The treatment of pulps consisting of very fine fractions is often very difficult, very slow, and very energy-consuming, particularly where one wishes to obtain the dry matter contained therein at a high level of dryness. Accordingly, industry has long sought a drying method that does not have the above-mentioned disadvantages and that reduces the cost of treatment of these materials. A natural drying process whereby evaporation of the water by exposure of the pulp to the atmosphere would be desirable. Techniques of this kind have been used since time immemorial by salt makers who produce, in this way, an important part of the table salts consumed throughout the world.
However, a simple transfer of the techniques of the salt maker to the aforementioned pulps does not provide a satisfactory result. Problems arise, the solution of which have proven to be very difficult. In particular, one can observe that, in the case of products that have reached an almost acceptable degree of dryness, rain may bring about a rehydration and, in that way, cause a considerable loss of time. Moreover, in certain regions, precipitation occurs so frequently and so abundantly that it is practically impossible to dry a pulp in accordance with this technique.
Thus a need has continued to exist for techniques for spreading and for the construction of drying beds, or in other words spreading pans, that make possible for the rain water to flow off without rehydrating the dried pulp.